A major type of heart disease is valvular insufficiency, also called valvular regurgitation, which is characterized by the improper closing of a heart valve. A heart valve consists of a number of leaflets—either two or three—that swing open to allow blood to flow forward (anterograde) out of a heart chamber, and then swing closed to form a tight seal, preventing blood from leaking backwards (retrograde). Valvular insufficiency may result from a variety of problems with the components which make up the valve—for example, the leaflets themselves may degenerate, the tissue cords which tether the leaflets to muscles within the heart may break, or the ring of tissue within which the valve is seated (called the “annulus”) may expand after heart attacks or from congestive heart failure. Each of these problems leads to a common element in valvular regurgitation: when closed, the edges of the valve leaflets no longer fit snuggly next to each other and allow retrograde flow.
Mitral regurgitation (MR) (insufficiency of the valve which connects the left atrium with the left ventricle of the heart) and tricuspid regurgitation (insufficiency of the valve which connects the right atrium with the right ventricle of the heart) contribute significantly to cardiovascular morbidity and mortality. MR is a debilitating disease that can lead to serious complications and possible death. Its symptoms include shortness of breath, rapid respirations, palpitations, chest pain, and coughing. MR also leads to infective endocarditis, heart failure, pulmonary edema, stroke, arterial embolus, and arrhythmias, including atrial fibrillation and lethal ventricular arrhythmias. Detection and prompt effective treatment of MR leads to higher survival rates, decreased complications, and increased comfort for patients.
Currently, the only method of definitively repairing valvular regurgitation is open-heart surgery: In this procedure, the patient is first anesthetized and then subject to a thoracotomy. Access to the patient's heart is achieved by making a large incision, retracting the skin, muscle, and bony structures. The surgeon must stop the beating of the heart and cut it open to directly visualize the valve. The surgeon then may repair the valve surgically, or remove the valve and implant a prosthetic valve replacement. This requires placing the patient on cardiopulmonary bypass, which is a machine that circulates oxygenated blood throughout the body in place of the working heart and lungs.
Although open-heart surgery is a successful method of repairing or replacing faulty heart valves, it poses a significant risk to the well being of the patient, including death, severe injury, and disability. There is a risk of ischemic or other damage to the heart and other vital organs resulting from the discontinuance of the heart's normal function. The heart-lung machine may also cause abnormalities of the patient's circulatory, respiratory, hematologic and neurologic systems. There is a risk of stroke and other consequences from emboli released into the blood during the surgery and during initiation of cardiopulmonary bypass. There is a risk of heart attack. Significant damage occurs to the tissues and bone retracted from the patient's chest while gaining access to the heart. Post-operative complications such as wound infection, pneumonia, and venous thrombosis occur because of the extent of incisions and the patient's debilitated state. Consequently, a patient's recovery can be painful, discomforting, long in duration, and costly.
A minimally invasive, beating-heart procedure that would not expose the patient to these risks is therefore desirable. Moreover, a limited surgical approach or percutaneous approach would decrease or eliminate the tissue trauma that occurs from the extensive incisions of open-heart surgery, sparing patients pain, improving recovery time, and decreasing post-operative complications.
A very large population exists that would benefit from an alternative method of valve repair. Approximately 10% of coronary artery bypass surgeries include mitral valve repair or replacement, which amounts to 75,000 to 100,000 of such procedures per year world-wide. In addition, significant MR and/or TR complicate 30-60% of patients with congestive heart failure, contributing to their impaired cardiac function and causing significant morbidity. However, because of the significant risks involved in open-heart surgery, many of the patients are unable to undergo valve repair. Thus, a successful percutaneous or minimally-invasive method of valve repair on the beating heart would have extraordinary clinical benefit.
No one, however, has successfully repaired the mitral valve of the human heart with a minimally invasive, beating-heart procedure. Several factors are responsible for this. First, the heart and its associated valves are not directly visualized or accessible. One can use imaging techniques such as fluoroscopy or echocardiography, but these provide a two-dimensional image and a limited field of view. Second, it is extremely difficult to immobilize the rapidly moving heart valve leaflets for repair purposes while the heart is beating. Not only are the leaflets moving back and forth rapidly, but also they each have a different shape and geometry. Thus, no single device or methodology has successfully been used to repair heart valves in a minimally invasive manner on a beating heart.
One method of surgical repair of the mitral valve, called the “bow-tie” repair (also referred to as the “edge-to-edge” repair), especially lends itself to a percutaneous or minimally-invasive approach. In this technique, the patient is placed on cardiopulmonary bypass, the heart is stopped and incised to expose the mitral valve apparatus, and a single edge-to-edge suture is placed through the edges of the valve leaflets, thereby apposing the anterior and posterior leaflets and resulting in a “double-orifice” valve. This surgical technique has led to satisfactory reduction of mitral regurgitation (MR) with few re-operations and excellent hemodynamic results. A successful minimally-invasive or percutaneous device and method that would allow for the placement of such a suture or another apposing element by remotely manipulating a fastening device through the moving valve leaflets of the beating heart in a reliable and predictable manner would be a medical breakthrough.
There are several obstacles that such a device must overcome. Each valve leaflet moves independently, swinging open and closed as many as 40 to 120 times a minute (or 1 to 2 times a second). Blood is surging back and forth through the valve at velocities often greater than 3 meters per second. Each valve leaflet has a different shape, for example, the anterior leaflet of the mitral valve is long and relatively narrow, while the posterior leaflet is shallow and wide. The valve apparatus on the ventricular side of the valve—consisting of primary, secondary, and tertiary chordae tendinae and the papillary muscles—makes the manipulation of devices in this area difficult, and consequently the successful deployment of the device requires correctly negotiating the pathway through the valve without becoming entrapped within the cardiac structures and/or damaging them. The suture or “fastener” must incorporate enough leaflet tissue to prevent leaflet tearing and secure leaflet capture at the optimal location.
A number of patents describe devices and methods for placing a suture within tissue at a distance. U.S. Pat. No. 6,206,893 details a device and method for suturing of internal puncture sites, and U.S. Pat. No. 6,117,145 provides a method and device for providing hemostasis at vascular penetration sites. These patents describe devices and methods for stitching a suture through a punctured blood vessel from a remote site that is not under direct visual observation and thereby apposing the edges of the blood vessel wall. These described methods and devices are insufficient for properly and optimally capturing and fastening cardiac valve leaflets, because they do not describe methods or apparatuses that are sufficient to ensure the proper alignment with intracardiac structures, the independent immobilization of the mobile valve leaflets, and the fastening of tissues with specific leaflet geometry.
A number of patents address minimally invasive or percutaneous mitral and tricuspid valve repair, utilizing a variation of the concept of a “suture at a distance” derived from the open-heart “bow-tie” technique. U.S. Pat. No. 6,165,183 describes an approach to valve repair involving the performance of an edge-to-edge fastening of opposing heart valve leaflets through a catheter entering the heart. This patent describes a catheter to place a clip button on the two leaflets, and describes various embodiments of ways a clip can fasten two pieces of tissue together at a distance. No attention is paid however to the requirements of placing the clip within a cardiac valve of a living patient, specifically, how moving valves can be grasped and immobilized; how the device is oriented with regard to the asymmetric leaflets and other cardiac structures so that a proper clip position is obtained; and a remedy for improper clip position. Thus, U.S. Pat. No. 6,165,183 does not describe a clinically feasible device or method for cardiac valve repair. U.S. Pat. No. 6,269,819 describes “an apparatus for the repair of a cardiovascular valve having leaflets comprising a grasper capable of grabbing and coapting the leaflets of the valve.” It is based on the concept of a “bow-tie” repair performed at a distance. There is no description of a methodology of placing the device across the valve and avoiding cardiac structures. There is no description of how the grasper—which essentially pinches the two leaflets together—can simultaneously catch the two independently, rapidly moving leaflets in a reliable fashion or at the optimal location, other than on the stopped heart with the patient on cardiopulmonary bypass. As such, U.S. Pat. No. 6,269,819 does not provide a clinically feasible or optimal approach to minimally invasive valve repair.